Evaluating the NOAA Coastal and Marine Ecological Classification Standard in estuarine systems: A Columbia River Estuary case study

A common first step in conservation planning and resource management is to identify and classify habitat types, and this has led to a proliferation of habitat classification systems. Ideally, classifications should be scientifically and conceptually rigorous, with broad applicability across spatial and temporal scales. Successful systems will also be flexible and adaptable, with a framework and supporting lexicon accessible to users from a variety of disciplines and locations. A new, continental-scale classification system for coastal and marine habitats—the Coastal and Marine Ecological Classification Standard (CMECS)—is currently being developed for North America by NatureServe and the National Oceanic and Atmospheric Administration (NOAA). CMECS is a nested, hierarchical framework that applies a uniform set of rules and terminology across multiple habitat scales using a combination of oceanographic (e.g. salinity, temperature), physiographic (e.g. depth, substratum), and biological (e.g. community type) criteria. Estuaries are arguably the most difficult marine environments to classify due to large spatio-temporal variability resulting in rapidly shifting benthic and water column conditions. We simultaneously collected data at eleven subtidal sites in the Columbia River Estuary (CRE) in fall 2004 to evaluate whether the estuarine component of CMECS could adequately classify habitats across several scales for representative sites within the estuary spanning a range of conditions. Using outputs from an acoustic Doppler current profiler (ADCP), CTD (conductivity, temperature, depth) sensor, and PONAR (benthic dredge) we concluded that the CMECS hierarchy provided a spatially explicit framework in which to integrate multiple parameters to define macro-habitats at the 100 m² to >1000 m² scales, or across several tiers of the CMECS system. The classification's strengths lie in its nested, hierarchical structure and in the development of a standardized, yet flexible classification lexicon. The application of the CMECS to other estuaries in North America should therefore identify similar habitat types at similar scales as we identified in the CRE. We also suggest that the CMECS could be improved by refining classification thresholds to better reflect ecological processes, by direct integration of temporal variability, and by more explicitly linking physical and biological processes with habitat patterns.     

Sedimentation within and among mangrove forests along a gradient of geomorphological settings

Coastal wetlands provide important ecological services to the coastal zone, one of which is sediment retention. In this study we investigated sediment retention across a range of geomorphological settings and across vegetation zones comprising coastal wetlands. We selected six coastal wetlands dominated by mangroves over a gradient from riverine to tidal settings in Southeast Queensland, Australia. Each site was comprised of three distinct vegetation communities distributed as parallel zones to the coast line: seaward fringe mangroves, landward scrub mangroves and saltmarsh/ cyanobacteria mat of the high intertidal zone. We measured suspended sediment retention and sedimentation rates. Additionally, in order to assess the origin of sediment transported and deposited in the mangroves, glomalin, a novel terrestrial soil carbon tracer, was used. Our results show a mean average sedimentation of 0.64 ± 0.01 mg cm⁻² spring tide⁻¹, which was variable within sites, regardless of geomorphological setting. However, geomorphological setting influenced spatial patterns of sediment deposition. Riverine mangroves had a more homogeneous distribution of sediments across the intertidal zone than tidal mangroves, where most sedimentation occurred in the fringe zone. Overall, the fringe zone retained the majority of sediment entering the coastal wetland during a tidal cycle with 0.90 ± 0.22 mg cm⁻² spring tide⁻¹, accounting for 52.5 ± 12.5% of the total sedimentation. The presence of glomalin in suspended sediments, and thus the relative importance of terrigenous sediment, was strongly influenced by geomorphological setting, with riverine mangroves receiving more glomalin in suspended solids than tidal mangroves. Glomalin was also differentially deposited within the vegetation zones at different geomorphological settings: primarily at the fringe zone of tidal mangroves and within the scrub zone of riverine mangroves. The differences we observed in the spatial distribution of sedimentation and the difference in the origin of the sediment deposited in riverine and tidal mangroves are likely to have an impact on ecological processes.     

Slow steps towards management of the world's largest tuna fishery

Today, the tuna fishery of the western and central Pacific is one of the world's largest fisheries. Annual catches exceed 2 million mt—approximately 50% of the global tuna catch—with an estimated landed value of USD 3 billion (in 2005). The fishery expanded rapidly from the mid 1980s, following the development of the purse-seine fishery. From the mid 1990s, it was recognised that a Regional Fisheries Management Organisation was required to facilitate cooperation in the management of the resource. Following almost a decade of negotiations and planning, the Western and Central Pacific Fishery Commission (WCPFC) was established in 2004. During the interim period, stock assessments for the key tuna species were developed and revealed that for two species (yellowfin and bigeye tuna) there was concern regarding the increased levels of fishing mortality. However, declarations and resolutions calling for restraint in the expansion of fishing effort were largely unheeded over the last decade and, to date, the WCPFC has been unable to introduce any measures to effectively reduce (or limit) the level of fishing mortality on yellowfin and bigeye tuna. This paper proposes a number of mechanisms for improving the performance of the WCPFC with respect to meeting the conservation and management objectives of the commission and argues that Pacific Island nations need to collectively take the lead to ensure the effective management of the resource.     

Recent sediments of the southwestern Barents Sea

The paper is based on textural, mineralogical and chemical studies of surface and subsurface sediments from 80 stations in the southwestern Barents Sea. Dispersed phases are quantitatively insignificant in these oxic shelf sediments and it is argued that the deposits are predominantly terrigenous in origin. A combined analysis of the mineralogy and chemistry of the separated size fractions allows the recognition of petrographic provinces. The patterns of sediment dispersal are discussed. The coarsest components of the Barents Sea sediments are of local origin whereas long-distance transport of finer material is taking place.     

The mantle,CO2 and the giant Aptian chemogenic lacustrine carbonate factory of the South Atlantic: Some carbonates are made,not born

During the Aptian (Cretaceous), in what is now the South Atlantic, the largest chemogenic (abiotic) carbonate factory so far identified in the Phanerozoic geological record developed as a vast hyper-alkaline lake system. This covered at least 330 000 km², producing carbonates, locally over 500 m thick, in what are now the offshore Santos and Campos basins (Brazil), and Kwanza Basin (Angola). Current evidence supports the view that almost all of this carbonate was chemogenic in origin, precipitated from hyper-alkaline, shallow lake waters, probably by evaporation. This unit, best documented from offshore Brazil and known as the Barra Velha Formation (Santos Basin) and the Macabu Formation (Campos Basin), consists of just two basic carbonate components, millimetre to centimetre sized crystal shrubs and spherulites. These are commonly in situ but can also be reworked into a range of detrital facies. Demonstrable microbialites are generally rare. These carbonates are associated with Mg silicates (as clays) which had a profound influence not only on the textural development of the in situ carbonates, but also on their diagenesis. The dissolution of the clays produced much of the porosity in these limestones, which are the hosts for multi-billion barrel oil fields. The source of the carbonate was most likely from metasomatic alteration of mafic rocks, such as continental flood basalts related to Atlantic opening, with some contribution from much older continental basement. Clear evidence that serpentinization of possible exhumed mantle is lacking but mantle CO₂ is likely to have been a critical factor in determining the composition of the fluids from which the carbonates formed and the high alkalinities of the lake waters.     

Alteration minerals,fluids, and gases on early Mars: Predictions from 1‐D flow geochemical modeling of mineral assemblages in meteorite ALH 84001

Clay minerals, although ubiquitous on the ancient terrains of Mars, have not been observed in Martian meteorite Allan Hills (ALH) 84001, which is an orthopyroxenite sample of the early Martian crust with a secondary carbonate assemblage. We used a low‐temperature (20 °C) one‐dimensional (1‐D) transport thermochemical model to investigate the possible aqueous alteration processes that produced the carbonate assemblage of ALH 84001 while avoiding the coprecipitation of clay minerals. We found that the carbonate in ALH 84001 could have been produced in a process, whereby a low‐temperature (~20 °C) fluid, initially equilibrated with the early Martian atmosphere, moved through surficial clay mineral and silica‐rich layers, percolated through the parent rock of the meteorite, and precipitated carbonates (thereby decreasing the partial pressure of CO₂) as it evaporated. This finding requires that before encountering the unweathered orthopyroxenite host of ALH 84001, the fluid permeated rock that became weathered during the process. We were able to predict the composition of the clay minerals formed during weathering, which included the dioctahedral smectite nontronite, kaolinite, and chlorite, all of which have been previously detected on Mars. We also calculated host rock replacement in local equilibrium conditions by the hydrated silicate talc, which is typically considered to be a higher temperature hydrothermal phase on Earth, but may have been a common constituent in the formation of Martian soils through pervasive aqueous alteration. Finally, goethite and magnetite were also found to precipitate in the secondary alteration assemblage, the latter associated with the generation of H₂. Apparently, despite the limited water–rock interaction that must have led to the formation of the carbonates ~ 3.9 Ga ago, in the vicinity of the ALH 84001 source rocks, clay formation would have been widespread.     

Writing difference differently

This paper investigates the writing of situated knowledge and explores the possibilities of enacting difference by writing differently. We present a selection of research stories in which carrier bags, sounds, baskets, gardens and potatoes are interpreted less as objects of research or metaphors to aid in analysing phenomena, than as mediators of the stories. Our stories emphasise the ontological politics of engaging with and representing the relational, the messy, the spontaneous, the unpredictable, the non‐human and bodily experiences. These stories demonstrate how writing is performative and how it is integral to the production of knowledge.     

Prediction of L-band signal attenuation in forests using 3D vegetation structure from airborne LiDAR

In this study, we propose a novel method to predict microwave attenuation in forested areas by using airborne Light Detection and Ranging (LiDAR). While propagating through a vegetative medium, microwave signals suffer from reflection, absorption, and scattering within vegetation, which cause signal attenuation and, consequently, deteriorate signal reception and information interpretation. A Fresnel zone enveloping the radio frequency line-of-sight is applied to segment vegetation structure occluding signal propagation. Return parameters and the spatial distribution of vegetation from the airborne LiDAR inside Fresnel zones are used to weight the laser points to estimate directional vegetation structure. A Directional Vegetation Density (DVD) model is developed through regression that links the vegetation structure to the signal attenuation at the L-band using GPS observations in a mixed forest in North Central Florida. The DVD model is compared with currently-used empirical models and obtained better R² values of 0.54 than the slab-based models. Finally, the model is evaluated by comparing with GPS observations of signal attenuation. An overall root mean square error of 3.51 dB and a maximum absolute error of 9.38 dB are found. Sophisticated classification algorithms and full-waveform LiDAR systems may significantly improve the estimation of signal attenuation.